It operates if plugged in. Flow rate is adjusted by piston stroke length. I have plugged pump in and verified it spins, with no unusual noises or vibrations. Pump is 120V. This pump is used.
This is a companion discussion topic for the original entry at https://www.ebay.com/itm/FMI-Lab-Pump-Model-QSY-Tested-120V-/143754203803